Survey on stored rice insects in Makassar, Indonesia: a preliminary study

Stored-product insects in rice are threats to the quality and quantity of stored rice. One of the methods to monitor insects in the storage facility is using an ultraviolet (UV) light trap. This study aimed to investigate the species diversity and abundance of insects trapped using UV light traps in the government’s stored rice in Makassar City, Indonesia. This study was conducted in a rice storage maintained by the Indonesian Bureau of Logistics (Bulog) Panaikang in early October 2022. Six UV light traps (4 watts) were hung (h=1.8 m) on four sides of a rice pile. Trapped insects were counted and identified. Results showed that the insects trapped by the UV light traps belonged to three orders, i.e., Coleoptera, Lepidoptera, and Hymenoptera. Cryptolestes ferrugineus (Stephens) (Laemophloeidae), Tribolium castaneum (Herbst) (Tenebrionidae), and Rhyzopertha dominica (Fabricius) (Bostrichidae) were three dominant coleopteran species trapped by UV light traps. The diversity was intermediate (H’=1.17), while the dominance (D=0.66) was high, and evenness (E=0.38) was low. Those species are classified as major pests due to their potential to cause economic damage to grains and products.


Introduction
Rice is the staple food for a vast majority of people in Southeast Asia, including Indonesian.Proper postharvest handling plays an important role in maintaining the quality and quantity of postharvest products.The postharvest process includes various actions taken from processing the harvest to storing postharvest products.Production of agricultural commodities is generally seasonal and exposed to the natural environment.However, postharvest handling is very important, so it plays a role in determining the stability of the food supply chain.Quantitative losses of postharvest products are economically occurring in the field (15%), processing (13-20%), and in storage (15-25%) [1].
Rice storage is a postharvest process that aims to maintain the availability of food, provide seeds, and maintain price stability.One of the main problems encountered in the storage process is the potential attack of postharvest pests.Stored rice in the long-term has the opportunity to be infested with various 1230 (2023) 012096 IOP Publishing doi:10.1088/1755-1315/1230/1/012096 2 types of insects that can be potentially as pests.The infestations can reduce the quality and quantity of rice as human food and seed.
One of the monitoring techniques of insects in the storage facility is using an ultraviolet (UV) light trap [8,9].Conditions of the storage facility is one of the factors that plays an important role in maintaining the quality and quantity of stored rice.Storage facility conditions can affect the population of insects and their diversity.This study aimed to investigate the species diversity and abundance of insects trapped by using ultraviolet light traps in the government's stored rice in Makassar City, Indonesia.

Materials and Methods
Insects samples were collected from a rice storage maintained by the Indonesian Bureau of Logistics (Bulog) Panaikang, Makassar, South Sulawesi, Indonesia in early October 2022.Six Krisbow ® ultraviolet light traps (4 watts) were hung (h=1.8 m above the ground) on four sides of a rice pile for 72 hours (Figure 1).Trapped insects in UV light traps were sorted and identified at the Laboratory of Pest, Department of Plant Pests and Diseases, Faculty of Agriculture, Universitas Hasanuddin.Collected insects were identified based on morphological characteristics.The Olympus SZ61 trinocular stereo microscope and Nikon Eclipse E100 compound microscope were used to determine the insect samples according to the available literature [10,11].The Dino-Lite Edge AF4915 Series digital microscope was used to document the insect samples.
Insect diversity was analyzed using the biological diversity indices [12].The level of insect diversity was calculated by using the Shannon-Wiener index.The level of dominance was calculated by using the Simpson index.The level of evenness was calculated by using the Shannon evenness index.All analyses were done by using Microsoft Office Excel 16.16.27version.

Results and Discussion
In total, 3,263 of insect individuals were collected at rice storage in Makassar (Table 1).They belong to 22 (morpho)species, 15 genera, and three orders.Coleoptera was the most diverse and abundant order with 18 species and 3,249 individuals.Based on the indices, the diversity was at an intermediate level (1.17), while the dominance (0.66) was considered high, and the evenness (0.38) level was considered low [12].Compared to the previous studies, the diversity was higher than in rice storage at Klang Selangor, Malaysia [13] and maize storage at Sumbawa District, Nusa Tenggara Barat, Indonesia [14].The rusty grain beetle, Cryptolestes ferrugineus was the most abundant insect (1,421 individuals) (Figure 3a).The rust red flour beetle, Tribolium castaneum was the second abundant insect (1,071 individuals) (Figure 3b).Adults of T. castaneum secreted benzoquinones compounds that may cause consumer rejection due to the unpleasant odors in the commodity [10].These two species (C.ferrugineus and T. castaneum) are the secondary pests that feed on already damaged grain and commonly attack rice and other grains [2,15,16].
The lesser grain borer, Rhyzopertha dominica was the third abundant insect (708 individuals) (Figure 3c).This species is a primary pest and an internal feeder on whole grain of rice [15,17].Those three species of pests that were most abundant are the cosmopolitan species found worldwide, from temperate to tropical countries [2,18].This study found numerous holes and white powder on the outer surface of woven plastic sacks during traps installation (Figure 4).The lesser grain borer, R. dominica has been 4 categorized as a penetrator of packaging that could penetrate the packaging by creating holes as an entranceway through the packaging [19,20].The Angoumois grain moth, Sitotroga cerealella was found in a few numbers (5 individuals) trapped by UV light trap.This species is a primary pest and internal feeder of rice seed [21].The presence of this insect might be initiated from the milling process of the whole kernel that has not been wellprocessed and infested previously into the stored rice grain.
The hairy fungus beetle, Typhaea stercorea was found in a few numbers (27 individuals) trapped by UV light trap.The presence of this species was an indicator of grain quality loss and fungal growth in the storage [22].This species is mainly mycetophagous (fungal feeder) and was reported to complete their life cycle when reared on Aspergillus flavus, Eurotium rubrum, and Penicillium purpurogenum [23].
The sap beetles, Carpophilus sp. was found in a few numbers (8 individuals) trapped by UV light trap.In another study, Carpophilus spp. was one of the most abundant species found in paddy rice storage facility in Brazil [24].This species was attracted to molds and yeasts on commodity [10].
The lesser mealworm, Alphitobius diaperinus was found in a few numbers (2 individuals).This species is a fungal feeder, minor pest, and scavenger on a wide range of grains, exclusively in damp condition [10].This species secreted six quinones from abdominal glands and cause disagreeable odors in grains [10,25].
Some winged ant also attracted by UV light [26].Monomorium sp. was found in this study and is a generalized forager [27].Monomorium ant also has a generalized diet, even M. rothsteini is a granivorous ant [28].This genus considering cosmopolitan around the world and found in many terrestrial habitats and microhabitats [28].The ant's existence in storage is also important because they are potentially carrying fungi and bacterial pathogens [29,30].
The ground beetles, Carabidae family and the rove beetles, Staphylinidae family were found in a few numbers, 3 and 4 individuals, respectively.Six species of staphylinids were associated with storedproducts and in this family is mostly predaceous beetles [2,35,36]  The captured insects were dominated by coleopterans including three most abundant species, C. ferrugineus, T. castaneum, and R. dominica.Those species are categorized as major pests in rice storage.Besides insect pests, there were also some species of natural enemies such as parasitic wasp and predaceous beetles even in small numbers.

Figure 1 .
Figure 1.Design of ultraviolet light traps placement

Figure 3 .
Figure 3. Holes and rice powder by Rhyzopertha dominica attacks on the surface of a woven plastic rice sack 4. Conclusion UV light trap successfully captured 3,263 individuals and 22 species of insect in rice storage in Makassar.The diversity was intermediate, while the dominance was high and the evenness was low.The captured insects were dominated by coleopterans including three most abundant species, C. ferrugineus, T. castaneum, and R. dominica.Those species are categorized as major pests in rice storage.Besides insect pests, there were also some species of natural enemies such as parasitic wasp and predaceous beetles even in small numbers.

Table 1 .
Insects trapped by ultraviolet light trap in rice storage.